Methods and apparatus for rendering an optically encoded medium unreadable

ABSTRACT

Methods and apparatus are provided for making an optically readable media unreadable. The method includes steps of (a) providing the media with an optically activated mechanism that degrades the reflectivity of a surface wherein information is encoded; (b) exposing the media to optical radiation for reading out the information; and, during the step of exposing, (c) initiating the operation of the optically activated mechanism. In this embodiment the step of initiating includes steps of (d) generating singlet oxygen in a layer disposed on the media; and (e) reacting the singlet oxygen with a metal-containing layer for oxidizing the surface of the metal-containing layer, thereby degrading the reflectivity of the surface. In a further aspect the optically activated mechanism causes a defocusing of a readout beam, thereby degrading reflection of the readout beam from a surface wherein information is encoded. In another embodiment the method deforms a surface of the layer resulting in readout beam aberration or in an inability to correctly stay on track. In another embodiment a portion of the surface is removed to the atmosphere, such as by evaporation of sublimation. In this embodiment a layer of the media is comprised of a volatile component and at least one other component. Removing at least some of volatile component by evaporation or sublimation causes an increase in at least one of photoabsorption or scattering or surface roughness with the remaining component, thereby rendering at least a portion of encoded information of the media unreadable, or affecting the tracking operation.

CLAIM OF PRIORITY FROM A COPENDING PROVISIONAL PATENT APPLICATION

This application is a continuation of Ser. No. 09/338,959 Jun. 24, 1999,now U.S. Pat. No. 6,338,933.

Priority is herewith claimed under 35 U.S.C. §119(e) from copendingProvisional Patent Application No. 60/090,682, filed Jun. 25, 1998. Thedisclosure of this Provisional Patent Application is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

This invention relates to optically readable data storage media and,more particularly, to techniques to render said media unreadable afterbeing read at least once.

BACKGROUND OF THE INVENTION

It is often desirable when distributing software or other informationthat is recorded on a medium to insure that only one party is enabled toread the recorded information. For example, a company that sellscomputer software will find it advantageous to enable only the purchaserto read the software from a disk and transfer or install the software tocomputer memory, such as a hard disk, while preventing subsequent accessby other parties to the software. However, this has proven to be avexing problem that is not readily solved.

When the information is distributed on a read/write medium, such as theubiquitous floppy disk, it may be possible to cause the installationsoftware to erase all or part of the information after it has beensuccessfully installed. Unfortunately, such information may bedistributed on write-protected disks, thereby rendering such erasureimpossible. Also, any protection mechanism that relies on computersoftware to implement has the potential to be defeated by additionalcomputer software.

U.S. Pat. No. 5,815,484 discloses an optical disk having a reflectivemetallic layer with a plurality of data structures (pits and lands) anda reactive compound superimposed over at least some of the datastructures. The reactive compound is a photochromic compound whichchanges from an optically transparent condition to an optically opaquecondition when subjected to readout light and/or atmospheric oxygen. Thedarkening of the photochromic compound prevents a sufficient amount ofreadout light from being detected by the readout apparatus, therebyeffectively rendering the optical disk unreadable.

At least one perceived disadvantage of this approach is thatphotochromic darkening is often reversible, which could be used todefeat the technique.

OBJECTS OF THE INVENTION

It is a first object and advantage of this invention to provide animproved system and method to render an optically readable media, suchas, but not limited to, a laser disk, a compact disk (CD), or a digitalvideo disk (DVD), unreadable.

It is a second object and advantage of this invention to provide animproved system and method to render an optically readable mediapermanently unreadable, after having been read at least once.

It is a third object and advantage of this invention to provide anoptically activated mechanism that destroys or impairs the reflectivityof a metal-containing layer, thereby rendering an optically readablemedia unreadable.

It is a further object and advantage of this invention to provide anoptically activated mechanism that modifies a transparent layer so as tocause readout beam aberration, thereby rendering an optically readablemedia unreadable.

It is once further object and advantage of this invention to provide amechanism that relies on non-atmospheric oxygen, such as oxygenpreloaded into or generated within a layer of an optically readablemedia, for modifying the optical properties of the media so as to renderthe media optically unreadable.

It is still another object and advantage of this invention to provide amechanism that relies on an evaporative technique for modifying theoptical properties of an optically readable media so as to render themedia optically unreadable.

It is another object and advantage of this invention to provide amechanism that alters a surface characteristic of an optically readablemedia so as to detrimentally affect a readout apparatus tracking processduring an attempted readout of the media.

It is a further object and advantage of this invention to provide amechanism that causes surface topography changes to an opticallyreadable media so as to detrimentally affect a readout apparatusfeedback and tracking process, thereby adversely affecting the fidelityof the readout.

SUMMARY OF THE INVENTION

The foregoing and other problems are overcome and the objects and theadvantages of the invention are realized by methods and apparatus inaccordance with embodiments of this invention.

In one aspect this invention provides a method for making an opticallyreadable media unreadable during a play process. The method includessteps of (a) providing the media with an optically activated mechanismthat degrades the reflectivity of a surface wherein information isencoded; (b) exposing the media to optical radiation for reading out theinformation; and, during the step of exposing, (c) initiating theoperation of the optically activated mechanism. In this embodiment thestep of initiating includes steps of (d) generating singlet oxygen in alayer disposed on the media; and (e) reacting the singlet oxygen with ametal-containing layer for oxidizing the surface of the metal-containinglayer, thereby degrading the reflectivity of the surface. The step ofgenerating may include a step of diffusing the singlet oxygen through adiffusion barrier that is disposed between the layer and themetal-containing layer.

In a further aspect the optically activated mechanism causes adefocusing of a readout beam, thereby degrading reflection of thereadout beam from a surface wherein information is encoded.

In one embodiment the method generates an optical intensity gradient ina layer disposed on the media; and, in response to the generatedgradient, deforms a surface of the layer resulting in readout beamaberration and/or adversely affecting the tracking process, resulting inreadout degradation and a loss of fidelity. In this case the step ofproviding provides the layer so as to comprise an azobenzene-containingpolymer. In an alternate embodiment a surface layer may react with anatmospheric component, such as oxygen, so as to degrade the trackingprocess by inducing a surface topography change, without inducing anysignificant change in the light transmission properties of the surfacelayer.

In another embodiment the step of initiating includes steps of:irradiating a photocurable polymer region that comprises part of themedia; and, in response to the irradiation, photopolymerizing thepolymer, thereby changing an index of refraction of the polymerresulting in readout beam aberration.

This invention also encompasses optically encoded media that operate inaccordance with the foregoing methods, and that are constructed inaccordance with the techniques of this invention.

In accordance with further embodiments of this invention an opticallyreadable media has a patterned structure for encoding information thatcan be readout by application of light, and further includes a layerthat is comprised of a volatile component and at least one othercomponent. Removing at least some of volatile component by evaporationor sublimation causes an increase in at least one of photoabsorption orscattering with the remaining component, thereby rendering at least aportion of the encoded information unreadable. The other component caninclude a lactone dye, such as crystal violet lactone, and the volatilecomponent can be, for example, NMP (N-methyl pyrrolidinone). In afurther embodiment an organic material, such as CsF or KBr, is coated onthe surface of the disk and provides a surface haze when exposed towater vapor or carbon dioxide, thereby increasing the scattering anddecreasing the signal-to-nose ratio, and degrading the readout fidelity.

A method is disclosed for making an optically readable media unreadable.This method includes steps of (a) providing the media with a surfacelayer having a planar surface topography; and (b) subsequent to orduring a first readout of the optically readable media, modifying atleast a portion of the planar surface topography to a non-planar surfacetopography. This is accomplished by the use of at least one of aphotoresponsive polymer, a removal of a substance from the surface layerto the atmosphere, or by interaction with a substance in the atmosphere.This latter process may occur without significantly modifying atransparency of the surface layer to a readout beam. The deviation ofthe non-planar surface layer topography from the planar surface layertopography is sufficient to detrimentally affect at least a trackingoperation of a readout device that generates the readout beam.

BRIEF DESCRIPTION OF THE DRAWINGS

The above set forth and other features of the invention are made moreapparent in the ensuing Detailed Description of the Invention when readin conjunction with the attached Drawings, wherein:

FIG. 1 is a schematic diagram of a conventional optical scanning systemfor reading an optically readable disk that incorporates one or morefeatures of the present invention;

FIG. 2 is a schematic side elevation and partial cross-sectional view ofan optical scanning head of the optical scanning system scanning theoptically readable disk of FIG. 1;

FIGS. 3A and 3B are a first pair of enlarged partial cross-sectionalviews showing a portion of the optical disk in FIG. 2 according to afirst embodiment of the invention, specifically an optically deformablephotopolymer layer embodiment, wherein the portion of the disk is shownin FIGS. 3A and 3B both before and after, respectively, scanning by anoptical beam;

FIGS. 4A and 4B are a first pair of enlarged partial cross-sectionalviews showing a portion of the optical disk in FIG. 2 according to asecond embodiment of the invention, specifically an optically inducedreflectivity modification embodiment, wherein the portion of the disk isshown in FIGS. 4A and 4B both before and after, respectively, scanningby an optical beam;

FIGS. 5A and 5B are a first pair of enlarged partial cross-sectionalviews showing a portion of the optical disk in FIG. 2 according to athird embodiment of the invention, specifically an optically curedphotopolymer embodiment, wherein the portion of the disk is shown inFIGS. 5A and 5B both before and after, respectively, scanning by anoptical beam;

FIG. 6 is a flow chart diagrammatically depicting generation of singletoxygen in a photosensitizer layer of the optical disk shown in FIG. 2,according to the reflectivity modifying embodiment shown in FIGS. 4A and4B;

FIG. 7 illustrate a colorless lactone form (crystal violet lactone) andits cationic (colored) form, and is useful in explaining an embodimentof this invention that employs an evaporative method for rendering anoptically readable media unreadable; and

FIG. 8 is an enlarged cross-sectional view of a portion of an opticallyreadable media having a surface topography that is modified from aplanar profile, and which can be used to detrimentally affect thetracking operation of the readout device in accordance with theteachings of this invention.

DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown a schematic diagram of anoptical scanning system 1 for reading an optically readable disk thatincorporates one or more features of the present invention. Although thepresent invention will be described with reference to the embodimentsshown in the drawings, it should be understood that the presentinvention may be embodied in many forms of alternative embodiments. Inaddition, any suitable size, shape or type of materials or elementscould be used.

It should further be noted at the outset that as employed herein an“optically encoded” or “optically readable” media or medium is intendedto cover a number of various devices wherein data, audio and/or videoinformation is stored such that it can be readout when a lightbeam(either visible light or invisible light) is applied to the device. Suchdevices include, but are not limited to, laser disks, compact disks(CDs), CD-ROMs, and digital video or versatile disks (DVDs), as well ascertain kinds of tape. In general, the devices of interest to thisinvention incorporate some type of structure that is capable of alteringthe reflectivity of the device to the readout light such that a logic 1bit can be distinguished from a logic 0 bit. By rendering such a device“unreadable” it should be understood that it is not necessary to makethe entire device unreadable. For example, it may be necessary to makeonly a relatively small portion of a boot record or a directory ofcontents unreadable such that the entire device becomes unusable, orsuch that some predetermined portion of the device becomes unusable.Making the device unreadable may also encompass adversely affecting thereadout device optical feedback and tracking process, such as byaltering the surface topography. By example, in this case the readoutlaser focus adjustments may not be able to react quickly enough to thesurface profile changes, resulting in an inability to maintain thecorrect tracking. This has been found to manifest itself as “skipping”through a music segment of a compact disk, or to otherwise negativelyimpact the fidelity of the output.

The optical scanning system 1, which may be conventional inconstruction, generally comprises a disk drive 10 and an opticalscanning head 30. The disk drive 10 is generally adapted to move anoptically readable disk 20, such as a CD-ROM, relative to the opticalscanning head 30. In the embodiment shown in FIG. 1, the opticalscanning head 30 is located below the optical disk 20 for scanning alower surface of the disk, though in other embodiments the scanning headmay located to scan an upper surface of the disk. The scanning head 30is preferably held by a movable carriage or arm (not shown) so that thehead 30 may be moved relative to a center of the disk. For example, thescanning head may be able to translate radially relative to the centerof the disk 20 or circumferentially around the center of the disk. Inalternate embodiments, the optical scanning head may be fixedly heldrelative to the center of the optically readable disk. As the disk 20moves over the scanning head 30, the head reads optically readable datastructures 23 (see FIG. 2) disposed on the disk 20.

Referring still to FIG. 1, the disk drive 10 includes a motor 12, adrive shaft 14 and a disk support or chuck 16. The drive shaft 14operably connects the motor 12 to the chuck 16. Thus, when energized themotor 12 rotates the chuck 16 through the drive shaft 14. The chuck 16comprises appropriate holding means (not shown) to stably hold the disk20 thereon when the chuck 16 is rotated by the motor 12. The motor 12 isadapted to rotate the chuck 16 and the disk 20 held thereon atpredetermined speeds. The motor 12 may operate to rotate the disk 20 ata variable rotational velocity so that the disk presents a readingsurface to the scanning head 30 which moves at a constant linearvelocity. For example, as the scanning head 30 is radially translatedcloser to the center of the disk 20 on the chuck 16, the motor 12 spinsthe disk 20 at an increasing rotational velocity. Thus, the portion ofthe disk 20 passing over the scanning head 30 is moving at a constantlinear velocity. It is noted that in conventional laser disks, the datastructure is generally disposed in a single track spiralling from theedge of the disk towards the center which requires that the disk spin ata variable rate of rotation in order for the track to move at a constantlinear speed relative to the scanning head. By way of example, the diskdrive 10 may rotate a DVD at an appropriately increasing rate ofrotation to provide a linear velocity of about 3.5 m/sec over thescanning head 30.

Referring now to FIG. 2, the scanning head 30 generally includes a lightsource 32 and a photodetector 34. The light source 32 generates anddirects an incident or interrogating beam 100 of electromagneticradiation (also referred to herein as optical radiation) against theoptical disk 20. The optical disk 20 includes a reflective layer 22 withdata structures 23 formed thereon or therein. The interrogating beam 100of electromagnetic radiation directed against the optical disk 20 isreflected by the reflecting layer 22 as a reflected beam 102. Thereflected beam 102 is then detected by then photodetector 34 of theoptical scanning head 30. When the disk drive 10 rotates the disk 20relative to the scanning head 30, the interrogating beam 100 passes overthe data structures 23 on the reflective layer 22 of the disk. As theinterrogating beam 100 moves over the data structures 23, the datastructures modulate the reflected beam 102. The modulation in thereflected beam 102 is registered at the photodetector 34 of the scanninghead 30 and converted to electrical signals.

More particularly, and by way of example, the light source 32 mayinclude a laser diode 36 or other such suitable device for generatingthe interrogating beam 100 of optical radiation. The beam 100 generatedby the laser diode 36 may be directed through a quarter wave plate 40and through polarizing beam splitter 38 as shown in FIG. 2.Alternatively, the positions of the wave plate and beam splitter may bereversed so that the beam passes first through the beam splitter andthen through the wave plate. Also, the beam generated by the laser diode36 may be collimated by a collimator (not shown) before encountering thewave plate 40. After the interrogating beam 100 passes through the beamsplitter 38, the beam encounters an appropriate lens 42 which focusesthe interrogating beam 100 at a predetermined focal point. Theinterrogating beam 100 emitted by the light source 30 may have awavelength of about 650 nm, although the beam may have otherwavelengths. The interrogating beam 100 may be focused to a spot size ofapproximately 0.63 μm. The depth of focus of the beam 100 is about 0.99μm, though this depth may be adjusted as required. The interrogatingbeam 100 is modulated by an appropriate modulator (such as anacousto-optic or electro-optic modulator, not shown) to effect aresidence time per bit of between about 100-200 nsec. The laser diode 36is otherwise adapted to deliver approximately 1 mW of power on theoptical disk 20. The energy deposited per bit by the interrogating beam100 is about 200 pJ and the fluence of the beam on the focus spot isabout 50 mJ/cm². Therefore, the intensity of the interrogating beam 100on the focus spot is about 300 kW/cm². In alternate embodiments, thelight source may have any other suitable configuration to generate aninterrogating beam of electromagnetic radiation having appropriatecharacteristics for reading data structures from an optical disk.

Still referring to FIG. 2, the reflective layer 22 of the laser disk 20is disposed between an upper protective layer 24 and a lower layer 26.The construction of the lower layer 26 will be described in greaterdetail below with reference to the three preferred embodiments of thisinvention. The reflective layer 22 may be comprised of metal such asaluminum, though other suitable materials may be used, and which isformed by appropriate means to provide a reflecting surface 28 to theinterrogating beam 100. As mentioned previously, the reflective surface28 of layer 22 is encoded with information stored as data structures 23.The data structures 23 are adapted to change the reflected beam 102 whenthe interrogating beam 100 is incident on features of the datastructures 23. For example, the data structures 23 may comprise apattern of lands 25 and pits 27 formed in the reflective surface 28 ofthe optical disk 20. The lands 25 are raised portions on the reflectivesurface 28 of the optical disk. The pits 27 are depressed portions(relative to the lands 25) in the reflective surface 28 of the opticaldisk 20. For example, the individual pits 27 may have a width of about0.4 μm and a length of between about 0.4-1.9 μm, though the pits mayhave any other suitable length and width. In alternate embodiments, thedata structures formed in the reflective surface of the optical disk mayhave any other suitable features which change a quality of the reflectedbeam when the interrogating beam encounters these features. By way ofexample such features may be sequences of scarified and reflectivesurfaces or through holes in the reflective surface of the optical disk.

In the preferred embodiment, as shown in FIG. 2, the interrogating beam100 generated by the light source 32 is focused by the lens 42 such thatthe focal point is located at the ‘bottom’ surface of the pits 27 in thereflective surface 28 of the optical disk 20. When the interrogatingbeam 100 is incident on the surface of a pit 27, the interrogating beam100 is reflected by the pit surface as a reflected beam 102. Thereflected beam 102 passes through the lens 42 (now acting as acollimator for the reflected beam) and is then deflected by the beamsplitter 38 to strike the photodetector 34 in the scanning head 30. Whenthe interrogating beam 100 is instead directed at a land 25 of thereflective surface 28, a lesser amount of the beam 100 is reflected backto be detected by the photodetector 34. This is because the surface ofthe land is located at a different depth then the focal depth of theinterrogating beam 100.

Alternatively, the interrogating beam 100 generated by the light sourcemay be focused by the lens at the surface of the lands 25 and not thepits 27.

In either case, it can be appreciated that the change in reflectivitybetween two states (corresponding to whether the interrogating beam 100is incident on a pit 27 or on a land 25), provides a mechanism to encodebinary data (i.e., ones and zeroes) into the surface of the disk.

The preferred embodiments of the present invention will be describedhereafter only with reference to the case where the interrogating beam100 is focussed at the surface of the pits 27 in the reflective surface28 of the optical disk 20, though the teachings of this invention areequally applicable to the case where the interrogating beam is insteadfocussed at the surface of the lands 25.

Referring now to FIGS. 3A and 3B, there is shown an enlargedcross-sectional view of a portion A of the optical disk 20 in accordancewith a first embodiment of this invention. The optical disk 20 isconstructed so as to include a surface relief photopolymer layer 200.The surface relief photopolymer layer 200 is comprised of one or morepolymers, such as, by example, an azobenzene containing polymer. It isknown that an azobenzene containing polymer is capable of exhibiting asurface deformations in response to a presence of an optical intensitygradient.

Reference in this regard may be had to an article entitled “Gradientforce: The mechanism for surface relief grating formation in azobenzenefunctionalized polymers”, Applied Physics Letters, Vol. 72, No. 17, pps.2096-2098, Apr. 27, 1998, J. Kumar et al. The authors report on thederivation of a model for the formation of holographic surface reliefgratings in azobenzene functionalized polymers. Forces leading tomigration of polymer chains upon exposure to light in the absorptionband of an azo chromophore are attributed to dipoles interacting withthe gradient of the electric field present in the polymer material. Theauthors further report that an efficient trans-cis cycling in theazobenzenes allows cooperative movement of the chromophores under theinfluence of gradient forces.

In accordance with the teachings of this invention the surface reliefphotopolymer layer 200 is disposed on the optical disk 20 such that theinterrogating beam 100 passes through the layer 200 when the beam 100interrogates the data structures 23 on the reflective layer 22 of theoptical disk 20. The surface relief photopolymer layer 200 in this caseforms the lower layer of the optical disk 20. One surface 201 of thephotopolymer layer 200 interfaces on an adjoining layer of the opticaldisk 20 and the opposite surface 202 of the photopolymer layer is a freeor unconstrained surface (see FIG. 3A). In this preferred embodiment,the surface relief photopolymer layer 200 is deposited by appropriatemethods (e.g. spraying or spin distribution) directly against thereflective surface 28 of the reflective layer 22 in the optical disk 20.In alternate embodiments, the surface relief photopolymer layer may bedeposited on an intermediate substrate between the reflective layer ofthe optical disk and the photopolymer layer, such that again thephotopolymer layer has an unconstrained surface.

FIGS. 3A and 3B respectively show the surface relief photopolymer layer200 in an initial or undeformed condition, before exposure to theinterrogating beam 100, and then in a deformed condition after exposureto the interrogating beam 100 (FIG. 3B may not be drawn to scale). Thesurface relief photopolymer layer 200 is exposed to the interrogatingbeam 100 when the optical disk 20 is scanned by the optical scanninghead 30 (see also FIG. 2).

As shown in FIG. 3A, when the optical disk is first scanned and thesurface relief layer 200 is in an undeformed condition, theinterrogating beam 100 is focussed to penetrate through the surfacerelief layer 200 and be reflected as a reflected beam 102 from thesurface of the pits 27. Thus, the disk may be read in the normal manneras previously described. However, exposure of the surface reliefphotopolymer layer 200 to the interrogating beam 100 also causes adeformation 210 in the unrestrained surface 202′ of the photopolymerlayer 200, as shown in FIG. 3B. The outwardly protruding deformation 210in the photopolymer layer 200 changes an amount of polymer materialthrough which the beam must travel and, due at least to the fact thatthis additional material has an index of refraction that differs fromair, the interrogating beam 100 experiences beam aberration, resultingin a defocusing of the interrogating beam. This defocusing is sufficientto cause a change in the amount of reflected light that is received bythe photodetector 34, and to thus cause at least a portion of the diskto be read incorrectly, which is the desired result. As such, errors aregenerated in subsequent attempts to read the optical disk.

It has been observed that surface relief deformations, created opticallyor by the evaporative mechanism of this invention, of but a few hundrednanometers can be sufficient to cause an optical disk to becomeunreadable, or to significantly diminish readout fidelity due to inducedreadout beam tracking problems. More particularly, the interrogatingbeam 100 generated by the light source 32 of the scanning head 30 (seeFIG. 2) is focussed to penetrate through the undeformed surface reliefphotopolymer layer 200 and form a spot size of less than, for example, 1μmat the surface of the pits 27. The highly focussed interrogating beam100 creates a large optical intensity gradient of approximately 10⁹mW/cm³. The unconstrained surface 202 of the surface relief photopolymerlayer 200 undergoes surface relief modulation in response to opticalintensity variations in the Mw/cm² range over micron scale lengths (i.e.an optical intensity gradient of around 10 Mw/cm³). Thus, when subjectedto the high intensity gradient generated by the interrogating beam 100focussed at the surface of the pits 27, the unconstrained surface of thesurface relief photopolymer layer 200 undergoes large surfacedeformations 210 (see FIG. 3B). When the surface relief deformation 210in the surface 202′ grows to some threshold size, it causes anaberration of the interrogating beam 100 which is thus no longer focusedat the surface of the pits 27 with sufficient acuity to be reflected asa reflected beam 102 detectable by the photodetector 34 (see FIG. 2).This results in readout failure. The exposure time for the unrestrainedsurface 202 to form a surface deformation of the desired size to causeaberration of the interrogating beam is dependent on the polymer blendand viscosity of the of the surface relief layer 200. The polymer blendand viscosity of the photopolymer in the layer 200 may be selected suchthat surface relief deformations 210 of the desired size are formedimmediately after but not during application of the interrogating beam100 when reading the disk 20 for the first time. This in effect resultsin the disk being rendered unreadable after the disk is read one time.Alternatively, the polymer blend and viscosity of the surface relieflayer 200 may be selected to form the surface relief deformation ofdesired size after a predetermined number of applications of theinterrogating beam, which consequently renders the disk unreadable afterthe disk has been read the predetermined number of times. In this regardthe readout procedure can be modified so as to repetitively scan theinterrogating beam over the same portion(s) of the disk surface, therebyinsuring that the surface relief polymer will be affected.

In accordance with this embodiment of the invention, a method forrendering the optical disk 20 unreadable by a play process includes thesteps of: a) providing the optical disk 20 with a surface reliefphotopolymer layer 200 which undergoes surface deformation at anunconstrained surface in the presence of an optical intensity gradient,as can be generated by the interrogating beam 100; and b) irradiatingthe surface relief photopolymer layer with the interrogating beam 100for inducing at least one surface relief deformation in theunconstrained surface of the photopolymer layer. The surface reliefdeformation thus induced during the play process causes an aberration inthe interrogating beam, which prevents focussing of the interrogatingbeam at desired locations on the features of the data structures 23during subsequent readout processes. This results in a failure toreadout the data on the disk during a subsequent readout process.

FIG. 8 is an enlarged cross-sectional view of a portion of an opticallyreadable media 20 having a surface topography that is modified from aplanar profile, and which can be used to detrimentally affect thetracking operation of the readout device in accordance with theteachings of this invention. In this embodiment the planar surfacetopography is modified to the non-planar surface topography (not shownto scale in FIG. 8) by the use of a photoresponsive polymer as describedabove, or through one of the evaporative techniques described below, orby providing a surface layer that interacts with a substance in theatmosphere, such as oxygen, water vapor, or carbon dioxide. In thesecases it is not necessary to modify the transparency of the surfacelayer to the readout beam, such as by increasing its radiation absorbingproperties through a color change. Instead, the varying surfacetopography, and its deviation from the expected planar surface layertopography, is sufficient to detrimentally affect the tracking operationof the readout device.

Referring now to FIGS. 4A and 4B, there is shown an enlargedcross-sectional view of Section A′ of the optical disk 20′ in accordancewith a second embodiment of the present invention. The optical disk 20′in the second embodiment of the invention is substantially similar tothe optical disk 20 described previously with reference to FIG. 2,except as otherwise noted below. As seen in FIGS. 4A and 4B, in thissecond embodiment the optical disk 20′ includes an oxygen (O₂) loadedphotosensitizer layer 300. The photosensitizer layer 300 is disposed onthe optical disk 20′ such that the interrogating beam 100 passes throughthe photosensitizer layer 300 when the optical disk 20′ is being scannedby the optical scanning head 30 (see FIG. 2). The photosensitizer layer300 may be separated from the reflective layer 22′ of the optical disk20′ by a diffusion barrier 302. The lower surface 304 of thephotosensitizer layer 300 may be sealed from the environment by somemeans, such an impervious polymer layer.

When the optical disk 20′ is scanned with the optical scanning head 30,the interrogating beam 100 generated by the light source 32 passesthrough both the photosensitizer layer 300 and the diffusion barrier 302and is focussed at the surface of the pits 27′ in the reflective layer22′ of the optical disk. Correspondingly, the focussed interrogatingbeam 100 is then reflected from the reflective aluminum surface of thepits 27′ as a reflected beam 102 detectable by the photodetector 34 inthe scanning head 30 as mentioned previously (see FIG. 2). Irradiationof the photosensitizer layer 300 with the interrogating beam 100generates singlet oxygen (¹O₂) in the oxygen (O₂) loaded photosensitizerlayer 300. The highly reactive singlet oxygen (¹O₂) generated in thephotosensitizer layer 300 diffuses through the diffusion barrier to thereflective surface of the optical disk and reacts with the metal in thereflective surface so as to oxidize the reflective surface. Oxidation ofthe reflective surface, at least in the pits 27′ of the optical disk,degrades its reflectivity such that when the interrogating beam 100strikes the oxidized surface the reflection of the interrogating beam isdiminished. The decrease in reflectivity may be interpreted as thepresence of a land 25, and not a pit 27, thereby resulting in a readoutfailure, which is the desired result.

More specifically, and by way of example, the photosensitizer layer 300contains one or more photosensitizer compounds in combination with oneor more solvents, such as for example methanol, acetone, a 10%freon/ethanol mixture, or a 1% freon/ethanol mixture. The solventprovides a source of molecular oxygen (O₂) internal to thephotosensitizer layer 300.

Referring to FIG. 6, and in accordance with the present invention, acombination of the photosensitizer compound (PS) plus electromagneticradiation (i.e. light) having a wavelength of about 650 nm activates thephotosensitizer, wherein the activated photosensitizer may be indicatedas PS*. The activated photosensitizer then combines with non-atmosphericmolecular oxygen (O₂) to produce singlet oxygen (¹O₂). In thisembodiment of the invention, this reaction occurs within thephotosensitizer layer 300 upon application of the interrogating laserbeam 100, as when scanning the optical disk 20′. Hence, in the region ofthe photosensitizer layer 300 through which the interrogating beampasses, the photosensitizer compound becomes activated and combines withmolecular oxygen (O₂) provided from the solvent which is internal to thelayer 300 to produce the singlet oxygen (¹O₂). After generation in thephotosensitizer layer 300, the singlet oxygen (¹O₂) proceeds to diffusethrough the diffusion barrier 302 towards the reflective surface of oneor more of the pits 27′. The singlet oxygen (¹O₂) reaches the reflectivesurface and begins to chemically attack the metal after a delay timeT_(D). The delay time T₀ is sufficient to allow the interrogating beam100 to be reflected as reflected beam 102 by the surface of the pit 27′,and hence allow readout of the data encoded therein before the singletoxygen (¹O₂) attacks the pit surface. Thus, the diffusion barrier 302can be employed to delay oxidation of the reflective surface 28′ of theoptical disk until readout of the disk has been completed at least once.

The delay time T_(D) for the singlet oxygen (¹O₂) to diffuse through thediffusion barrier 302 depends on the thickness h of the diffusionbarrier 302 and the diffusivity D of the diffusion barrier to singletoxygen (¹O₂). The relation between the diffusion delay time T_(D) thethickness h and diffusivity of the barrier 302 is generally described bythe equation: $\begin{matrix}{T_{D} = \frac{h^{2}}{D}} & (1)\end{matrix}$

The diffusion barrier 302 comprises an appropriate medium which does notquench singlet oxygen (¹O₂) and has a controlled diffusivity D. Forexample, the diffusivity D of the diffusion barrier 302 may vary in arange from about 10⁻⁵ to 10⁻⁹ cm₂/sec depending on the material selectedfor the barrier 302. Therefore, the delay time T_(D) may be controlledto be greater than the time required to read the data encoded on thereflective layer 22′ of the disk 20′ by selecting a material with theappropriate diffusivity D and selecting an appropriate thickness h forthe diffusion barrier 302. However, the delay time T_(D) is constrainedby the lifetime (T₁) of singlet oxygen (¹O₂). The lifetime T₁ of singletoxygen (¹O₂) is a function of the hydrophobic and paramagneticproperties of the host. Examples of general lifetimes T₁ for singletoxygen (¹O₂) for different solvents are given below:

T₁ (μsec) Solvent   7 methanol  45 acetone  150 freon/ethanol (10%) 1400freon/ethanol (1%)

Thus the diffusion barrier 302 separating the photosensitizer layer 300from the reflective layer 22 of the optical disk is suitably sized toprovide a delay time T_(D) for singlet oxygen diffusion which is bothgreater than the readout time (T_(read)) and less than the lifetime T₁of singlet oxygen (¹O₂) (i.e. T₁>T_(D)>T_(read)).

Two suitable materials for the diffusion barrier 302 are polyurethane orTeflon™, while suitable materials for the photosensitizer layer 300include a pthalocyanine doped polymer, such as polycarbonate or PMMA, ora polymer doped with a porphyrin derivative, or other high triplet yielddye. Other suitable materials could be used as well, and thesespecifically listed materials should not be read in a limiting senseupon the practice of this invention.

Referring now to FIGS. 5A and 5B, there is shown an enlargedcross-sectional view of Section A″ of the optical disk 20″ in accordancewith a third embodiment of this invention. The optical disk 20″ in thisembodiment of the invention is substantially similar to the optical disk20 described previously with reference to FIG. 2, except as otherwisenoted below. As seen in FIGS. 5A and 5B, the optical disk 20″ inaccordance with this embodiment includes a substrate 400 which may beformed from a polycarbonate material disposed generally against thereflective surface 28″ of the reflective layer 22″ in the optical disk.Included between the substrate 400 and the reflective surface 28″ of thedisk 20″ are regions or pockets 402A, 402B of an uncured photopolymer402. As shown in FIG. 5A, the photopolymer 402 is disposed within thepits 27″ formed in the reflective layer 22″ of the optical disk 20″. Inan uncured state, the index of refraction of the photopolymer 402 issuch that the interrogating beam 100 generated by the light source 32(see FIG. 2) passes through both the substrate 400 and the uncuredphotopolymer 402, and the interrogating beam 100 is focussed at thesurface of the pits 27″. The uncured photopolymer 402 is adapted to cureafter illumination by light having a suitable wavelength, for exampleabout 650 nm, though the photopolymer may be adapted to cure whenirradiated with light having other wavelengths. Thus, illumination bythe interrogating beam 100 from the optical scanning head 30 (e.g.,laser light having a wavelength of about 650 nm) cures the photopolymer402 after a given time period (i.e., causes cross-linking between themolecules of the photopolymer, resulting in a change of viscosity and ageneral solidification of the photopolymer).

After the photopolymer cures, the index of refraction of thephotopolymer 402 changes such that the interrogating beam 100 directedat the pits 27″ and passing through the cured photopolymer 402′ (asshown in FIG. 5B) is no longer focussed at the surface of the pits 27″.That is, the curing of the photopolymer material results in beamaberration, and a loss of focus within the pit 27″. Therefore, inaccordance with this embodiment of the invention, illuminating theuncured photopolymer 402 in the pits 27″ of the optical disk 20″, aswhen reading the disk for the first time or during multiple passes afterthe initial reading, cures the photopolymer. After being cured thephotopolymer 402′, such as that disposed in the pits 27″, defocuses theinterrogating beam 100 such that it is no longer reflected as reflectedbeam 102 detectable by the photodetector 34. This in turn causes areadout failure, which is the desired result.

The uncured photopolymer 402 preferably has a curing time which allowsunencumbered first-time readout (i.e. the interrogating beam 100 isreflected by a pit 27″ as the reflected beam 102 that is detectable bythe photodetector 34 before the photopolymer cures) but preventssubsequent readout of the pit 27″.

Suitable photocurable polymers, such as acrylic resins, includewavelength sensitized resins, such as those used generally inphotolithography or in some rapid prototyping applications with, forexample, argon or krypton excitation lasers. General reference withregard to photopolymers may be had to the inventor's U.S. Pat. No.5,028,109, issued Jul. 2, 1991, entitled “Methods for FabricatingFrequency Doubling Polymeric Waveguides Having optimally EfficientPeriodic Modulation Zone and Polymeric waveguides Fabricated Thereby”.

Reference may also be had in the literature to other suitablephotoresponsive polymers, such as those mentioned in U.S. Pat. No.4,865,942, “Photohardenable Compositions Containing a Dye-Borate Complexand Photosensitive Materials Employing the Same”, by Gottschalk et al.

The foregoing three embodiments of this invention render an optical disk20, 20′, 20″ unreadable, or limit its viability to perhaps no more thanfour hours after first reading (i.e. playing) the optical disk with theoptical scanning system 1. Furthermore the three embodiments of thepresent invention accomplish this without rendering the optical disk 20,20′, 20″ susceptible to becoming unreadable prematurely from competingoptical conditions such as, for example, sunlight or indoor lighting.

Typical indoor lighting will generally not adversely affect theviability of the optical disk 20, 20′, 20″ in the three preferredembodiments of the present invention. However, should the possibleexposure to sunlight be of concern, then a narrow band filter material(not shown) may be deposited on the lower surface 26 of the disk toprevent sunlight activation of the polymeric medium(s) of choice.

It should be understood that the above description is merelyillustrative of the invention. For example, the step of directing theinterrogating beam may be performed by directing the beam at the opticaldisk for a continuous period of time sufficient to cause the reaction inthe photopolymer layer 200, 402 or photosensitizer layer 300.Alternatively, the interrogating beam may be directed at the disk indiscrete time periods which cumulatively trigger the reaction.Furthermore, the interrogating beam may be directed in discrete timeperiods during a single scan of the disk or over a multiple number ofscans of the disk.

A fourth embodiment of this invention will now be described. This fourthembodiment has the object of providing a method for disrupting anoptical signal such as that used in the reading of a DVD or CD byevaporation of a substance. This embodiment is thus also useful in theconstruction of optical disks that become unreadable after a period oftime.

This method provides a means of generating color, which is capable ofabsorbing an interrogating light beam, by evaporation of a substance.

By way of introduction, it is known that certain substances becomecolored or change color upon changes in solvent or environment. Anexample is the class of lactone dyes that are used in carbonless copypapers. The colorless lactone form of the dye can be caused to “open” tothe colored cationic form of the dye by absorption onto an acidic clayor other acidic substrate, by lowering of the pH of the lactone insolution, or by changing the polarity of the solvent in which thelactone is dissolved. The colorless lactone form and the coloredcationic form of an exemplary lactone dye, crystal violet lactone, isshown in FIG. 7.

Polymers derived from phenol and formaldehyde have been shown to beeffective in causing the opening of a lactone dye (see U.S. Pat. No.4,578,690), presumably due to the acidic nature of the phenoliccomponent. A test was performed using poly-p-(hydroxystyrene) obtainedfrom Hoechst-Celenese (Mw=6300) to determine if this polymer would alsocause crystal violet lactone to open and become colored. A solution ofthe polymer in THF was mixed with a small amount of crystal violetlactone and this solution was spotted on a glass plate and air dried.Upon drying a dark blue spot formed. It was observed that thepolymer-lactone solution remained colorless until the mixture was dried,whereupon the intense color of the cationic form of the dye formed.

This mechanism forms the basis of this embodiment of the invention, thatis, of using a mixture of solvents, one relatively volatile and a secondone which is relatively non-volatile, to prepare the polymer-lactonesolution. Upon drying of the solution, the less volatile solvent remainsupon evaporation of the more volatile solvent, and the mixture remainscolorless until the less volatile solvent evaporates over a period oftime. Mixtures of poly-p-(hydroxystyrene) (PHS), ethanol (as the morevolatile solvent), crystal violet lactone (CVL) and several lessvolatile solvents (LvS) were prepared. Drops of the mixtures wereallowed to air dry at room temperature and the color of the remainingfilms were noted to see what effect the less volatile solvent had uponcolor generation.

Preparation of the solutions: PHS ethanol CVL LVS color Solution #1 500mg 2.0 mL 20 mg 300 μL NMP −−− Solution #2 500 mg 2.0 mL 20 mg 300 μLTEGDME + Solution #3 500 mg 2.0 mL 20 mg 300 μL BA ++ Solution #4 500 mg2.0 mL 20 mg 300 μL THN +++ Solvent Name BP ° C. Z value NMP N-methylpyrrolidinone 202 65 TEGDME triethyleneglycol dimethyl ether 216 60 BAbenzyl alcohol 205 75 THN tetrahydronaphthalene 207 55 * ... denotes nocolor, +++ denotes intense color formation *The Z value is a measure ofrelative polarity. The values listed above are estimations.

From the above experiment, NMP was chosen as the best of the lessvolatile solvents tested since the polymer film remained colorless uponevaporation of the ethanol.

EXAMPLE #1

A solution of poly-p-(hydroxystyrene) (5 μm), ethanol (10 mL), crystalviolet lactone (200 mg) and NMP (3.0 mL) was prepared. A few drops wereapplied to a glass slide and the mixture was allowed to air dry at roomtemperature. The film which formed was soft and tacky to the touch butit was colorless. Color formation was followed over the course ofseveral days through the use of a spectrophotometer.

Time (hours) Optical Density (607 nm)  0 0 18 0.181 85 0.242

Since the film formed in example #1 was soft and tacky formaldehyde wasadded to cross link the phenolic polymer.

EXAMPLE #2

A solution of poly-p-(hydroxystyrene) (5 gm), ethanol (10 mL), crystalviolet lactone (220 mg), 28% ammonia (0.5 mL as a cross linkingcatalyst) and NMP (3.0 mL) was prepared. To this solution was added 37%aqueous formaldehyde (3.0 mL). A few drops were applied to a glass slideand the mixture was cured at about 65° C. on a hot plate until the filmwas hard. This took about 5 minutes. The film which formed was hard tothe touch and it was colorless after curing. Color formation wasfollowed over the course of several days through the use of aspectrophotometer.

Time (hours) Optical Density (607 nm)  1 0 24 0.270 50 0.315

EXAMPLE #3

To test the color stability of the system on storage, a film wasprepared as described in example #1. The air dried glass slide wassealed in a polyethylene zip-lock bag along with one drop of NMP to forma NMP saturated environment in the bag. The slide stored in this mannershowed no color formation after one week at room temperature. Uponremoval from the bag, color began to form as in examples 1 and 2. Theslide was dark blue with an optical density of 0.875 at 605 nm. afterfive days in the air at room temperature.

The scattering of light rather than absorbance can also be used toattenuate an optical signal. An evaporative method to cause increasedscattering can be achieved by mixing a polymer with a solid where thereis a mismatch between the refractive indexes of the two materials, andthen adding a solvent for the polymer which adjusts the refractive indexof the polymer-solvent mixture to match that of the solid. Under theseconditions the mixture is non-scattering or poorly scattering sincethere is a refractive index match between the polymer-solvent pair andthe solid. However, slow evaporation of the solvent causes a mismatchbetween the remaining polymer and solid and, therefore, the scatteringincreases.

EXAMPLE #4

A solution of 1.0 gm of cellulose acetate butyrate (CAB, Mw=70,000,13.5% acetyl, 37.5% butyryl, n=1.46) in 20 mL of ethyl acetate wasprepared and to this solution was added 1.0 gm of silica gel (70-230mesh, n about 1.50) and 600 μL of benzyl alcohol (n about 1.54). A dropof this mixture was placed on a glass slide and the ethyl acetate wasallowed to evaporate to provide a clear, transparent film through whichnews print could easily be read. Upon standing in the air for two daysthe film became quite cloudy and news print could be read through thefilm only with difficulty.

In accordance with the teachings of this invention, one or both of theforegoing evaporative-based methods can be used to render an opticallyreadable media, such as a DVD or CD, unreadable after a period of time.Referring by example to FIG. 2, the upper protective layer 24 could becomprised of one of the mixtures described in examples 1 and 2 above,which is initially colorless and transparent, but which becomes coloredand absorbing after sufficient solvent evaporation has occurred. Theupper protective layer 24 could also be comprised of the CAB-ethylacetate solution referred to in example 4, which is initially colorlessand transparent, but which becomes milky and scattering after sufficientsolvent evaporation has occurred. While it may be preferred to have thislayer exposed as a top-most layer, it is also within the scope of theinvention to apply an overlayer, so long as the overlayer issufficiently permeable to enable the evaporative process to occur.

It can be appreciated that this embodiment of the invention also doesnot require the presence of atmospheric oxygen, as the evaporation couldtake place as well in a vacuum, and neither does it require the presenceof a lightbeam to catalyze or initiate the process, as the color changeor increase in opacity and scattering can occur as well in a darkenclosure, so long as the evaporative process is not significantlyimpeded. Other methods for attenuation of an optical signal can also beemployed to practice this invention.

For example, it is well known that salts of a weak acid and a weak basein which either the acid or base or both are volatile will revert to thefree acid and free base upon standing in the open due to thevolatilization of one of the components. An example of this is the solidammonium carbonate, which slowly sublimes in the open due to theformation of the volatile components of the salt, ammonia and carbondioxide. This property may be used to generate color and thus opticalabsorption in several ways. For example, the salt of a volatile amineand a non-volatile acid component (carboxylic acid, phenol, etc.) may bemixed with a lactone dye, such as crystal violet lactone, or with an pHindicator dye. Volatilization of the basic (amine) component will leavethe acidic component behind. The acidic component may be used tocatalyze the opening of the lactone dye, or cause the color change in apH indicator.

The volatilization of a gas can also be used to generate a color. Forexample, a water damp polymer film containing a pH indicator dye may bestored in an atmosphere of a gas whose water solution is acidic (e.g.carbon dioxide, sulfur dioxide) or basic (ammonia, trimethylamine etc.)Upon removal of the film from the atmosphere the volatile gas willevaporate from the water damp film, and the pH will change causing acolor change in the pH indicator dye. This type of mechanism has beenused to detect carbon dioxide and amines (see Mills, et al. Anal. Chem1992, 64, 1383, Lakowicz et al., Biotechnol. Prog. 1998, 14, 326, andU.S. Pat. Nos. 5,183,763 and 5,846,836.)

The increase in absorbance or light scatter (or both) can beaccomplished by coating a chemically reactive layer, exemplified by thevarious examples given above, on the surface of a disk, using methodssuch as a spin coating, spraying, slot coating, or vacuum deposition.Patterned deposition can be done by a printing process, such as silkscreen or inkjet, or with masks using spray or vacuum coating.Alternately, the reactive layer may be prepared separately as anadherent plastic film, cut to size, and applied to the surface of thedisk.

Furthermore, the timed readout disablement can occur by increasingscattering from the interrogating laser beam, thereby degrading theoverall signal-to-noise ratio (SNR) level to an unacceptable level. Thisapproach is less sensitive to changes in laser power, error correctioncodes, or improved detector design.

Further by example, the vacuum deposition of thin layers of sensitiveinorganic materials, such as KBr or CsF, on the surface of the disk canprovide a surface haze when exposed to an atmospheric substance, such aswater vapor and/or carbon dioxide, thereby increasing at least one ofthe photoabsorption, the scattering, or the surface roughness, andthereby also decreasing the SNR.

Further by example, the evaporation of a volatile solvent from a polymercoating may lead to the precipitation of small scattering crystals, orthe evaporation could lead to a phase change of a polymer or polymermixture with concomitant light scattering.

Also, and as was discussed previously, the timed readout disablement canalso occur by lowering the reflectivity of the reflective metal coatedsurface(s) of the disk. This method is sensitive to the same factorsnoted above for the absorbance increase. It should be noted that thecorrosion of the buried reflective layer is essentially irreversible.

The adhesive layer in both CDs and DVDs can be modified to exploit thecorrosive effects of air on metals. Since a goal of the instantinvention is to provide short-lived disks, the use of differentmaterials is an option, compatible with manufacturability. Thecomposition of adhesive and plastic can be tailored to promote acorrosive reaction, once the disk packaging is removed. Also, thereflective layer itself can be made using metals more reactive thanaluminum, such as potassium or calcium.

This invention can be practiced by providing an optically encoded mediumwith two or more of the foregoing embodiments. For example, an opticaldisk can be constructed so as provide the surface deformation feature aswell as the aluminum layer oxidation feature, or theevaporatively-driven absorption and/or scattering change in combinationwith the reflective metal oxidation, thereby further ensuring theeffective destruction of the disk after being initially read.

Thus, various alternatives and modifications may be devised by thoseskilled in the art without departing from this invention. Accordingly,the present invention is intended to embrace all such alternatives,modifications and variances which fall within the appended claims.

What is claimed is:
 1. A method for intentionally making an opticallyreadable media unreadable by a play process, comprising steps of:providing the media with an optically activated mechanism that degradesthe reflectivity of a surface wherein information is encoded; exposingthe media to optical radiation for reading out the information; andduring the step of exposing, initiating the operation of the opticallyactivated mechanism; wherein the step of initiating comprises steps of,generating singlet oxygen in a photoresponsive layer disposed on themedia; diffusing the singlet oxygen through a diffusion barrier that isdisposed between the photoresponsive layer and a metal-containing layer;and reacting the singlet oxygen with the metal-containing layer foroxidizing the surface of the metal-containing layer, thereby degradingthe reflectivity of the surface.
 2. A method for intentionally making anoptically readable media permanently unreadable by a play process,comprising the steps of: providing an optically readable media with anoptically activated mechanism, said optically activated mechanisminterferes with the ability of the play process to read at least aportion of a data encoded reflective layer on said optically readablemedia, exposing the optically readable media to optical radiation forreading out information on said optically readable media, saidinformation encoded on said data encoded reflective layer; and duringthe step of exposing, initiating the operation of the opticallyactivated mechanism, wherein the step of initiating comprises:generating an optically intensity gradient in a layer disposed on theoptically readable media, wherein said layer comprises a first surfaceand a second surface, said first surface is unconstrained; and inresponse to the generated optical intensity gradient, deforming saidfirst surface of the layer, said first surface deformation making saidat least a portion of said data encoded reflective layer unreadable bythe play process.
 3. A method as in claim 2, wherein the step ofproviding provides the layer so as to comprise an azobenzene containingpolymer.
 4. A method as in claim 2, wherein the step of initiating iscomprised of steps of: irradiating a photocurable polymer region thatcomprises the media; and in response to the irradiation,photopolymerizing the polymer, thereby changing an index of refractionof the polymer resulting in readout beam aberration.
 5. An opticallyreadable media capable of intentionally being made unreadable by a playprocess, said media comprising an optically activated mechanism that isresponsive to light used to readout information for degrading thereflectivity of a surface wherein the information is encoded, whereinsaid mechanism is comprised of a photosenistizer compound for reactingwith oxygen molecules that are present within a second layer forgenerating singlet oxygen in the second layer, the singlet oxygenreacting with said data encoded reflective layer for oxidizing thesurface of said data encoded reflective layer, thereby degrading thereflectivity of the surface of said data encoded reflective layer.
 6. Anoptically readable media capable of intentionally being made unreadableby a play process, said media comprising an optically activatedmechanism that is responsive to light used to readout information fordegrading the reflectivity of a surface wherein the information isencoded, wherein said mechanism is comprised of a photosensitizercompound for reacting with oxygen molecules that are present within alayer for generating singlet oxygen in the layer, the singlet oxygenreacting with a metal-containing layer for oxidizing the surface of themetal-containing layer, thereby degrading the reflectivity of thesurface; the optically readable media further comprising a diffusionbarrier disposed between said layer and said metal-containing layer. 7.An optically readable media capable of intentionally being madepermanently unreadable by a play process, said media comprising: anoptically activated mechanism that is responsive to light used toreadout information from a data encoded reflective layer, said opticallyactivated mechanism defocuses a readout beam, thereby making at least aportion of said data encoded reflective layer unreadable by said readoutbeam, wherein said optically activated mechanism is comprised of a layerof polymer that is responsive to an optical intensity gradient generatedby said readout beam for deforming an unconstrained surface of saidlayer, resulting in readout beam aberration.
 8. A media as in claim 7,wherein said layer comprises an azobenzene containing polymer.
 9. Amedia as in claim 7, wherein said mechanism is comprised of at least oneregion comprised of photoresponsive polymer that is responsive to thereadout beam for being photopolymerized, thereby changing an index ofrefraction of the photocurable polymer resulting in readout beamaberration.
 10. A method for intentionally making an optically readablemedia permanently unreadable, comprising steps of: providing anoptically readable media with a data encoded reflective layer, said dataencoded reflective layer readable by a readout beam; providing theoptically readable media with a surface layer having a planar surfacetopography, said surface layer preceding said data encoded reflectivelayer in the optical path of the readout beam; and subsequent to orduring a first readout of the optically readable media, modifying atleast a portion of the planar surface topography to non-planar surfacetopography by the use of a photresponsive polymer and an opticalintensity gradient that interacts with the photresponsive polymer formodifying the planar surface topography to the non-planar surfacetopography, wherein a deviation of the non-planar surface layertopography from the planar surface layer topography is sufficient todetrimentally affect at least a tracking operation of a readout devicethat generates the readout beam.
 11. A method for making a limited playoptically readable media, said method comprising the steps of: providingan optically readable media with a data encoded reflective layer, saiddata encoded reflective layer readable by an optically readable mediareading device, said optically readable media reading device comprisinga reading beam; providing an optically readable media with an opticallyactivated mechanism, said optically activated mechanism comprising alayer with a first surface and a second surface, wherein said firstsurface is unconstrained, said layer preceding said data encodedreflective layer in the optical path of the reading beam of theoptically readable media reading device; wherein said opticallyactivated mechanism deforms said first surface of said layer in responseto said reading beam of said optically readable media reading device,said deformation inhibits the ability of said reading device to read atleast a portion of said data encoded reflective layer on said opticallyreadable media.